Fuel burner



Jfily 20, 1937. A. e. BLODGTT FUEL BURNER Filed June 21,. 1954 2 Sheets-Sheet 1 July 20, 1937.

A. a. BLODGETT FUEL BURNER Filed June 21, 1934 2 Sheets-Shet 2 Patented July 20, 1937 PATENT OFFICE FUEL BURNER Albert G. Blodgett, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Application June 21,

'7 Claims.

This invention relates to fuel burners, and more particularly to a burner having adjustable means for varying the cross-sectional area available for the discharge of the fuel into the furnace.

Pulverized fuel is ordinarily delivered to a burner in a stream of primary air, and secondary air is usually provided at the burner, the total air supply being sufficient to complete the combustion of the fuel. In many installations it is desirable to operate the furnace over a wide range of combustion rates as the demand for heat varies. For this purpose it is customary to control the supply of secondary air, reducing the rate of air flow when the fuel supply is decreased thus maintaining the correct ratio between the elements of combustion. Satisfactory results cannot be obtained at very low combustion rates, however, simply by reducing the secondary air,

, and for this reason apparatus has been developed which will reduce the primary air also by recirculating a part thereof through the pulverizer. Such apparatus is disclosed in the patent to Craig No. 1,951,862. For the best results in such a system it is necessary to use either a large and a small burner, or a single burner which is adjustable, so that the fuel stream may be projected into the furnace at a velocity above the rate of flame propagation even at low combustion rates. It is furthermore important to maintain ignition close to the burner nozzle, not onlyto prevent excessive flame length but also to heat the refractories adjacent the nozzle and obtain the benefit of heatradiated from these refractories to the fuel stream. 1

, While various types of adjustable burners have been proposed heretofore, none of them have proven satisfactory in actual practice. Some are complicated and expensive, and others are unable to withstand the high temperatures encountered.

It is accordingly one object of the invention to overcome these difficulties and provide a burner which will be simple and inexpensive to manufacture, durable and efficient in operation, and readily adjustable to vary the cross-sectional area of the fuel stream discharged therefrom.

It is a further object of the invention to providean adjustable fuel burner which will maintain ignition close to the burner nozzle, and particularly' to provide such aburner which will produce a short combustion flame having a high degree of turbulence.

It is a further object of the invention to provide a fuel burner which will not be easily obstructed by foreign particles, such as straw or 1934, Serial No. 731,715

rags, in the fuel stream, and which can be readily cleaned without interrupting the operation.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a vertical section through a pulverized fuel burner and the adjacent portion of'the furnace wall associated therewith, certain parts being shown in elevation;

Fig. 2 is an enlarged View of a portion of Fig. 1;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is a section on the line A-fl of Fig. 3, certain parts being shown in elevation;

Fig. 5 is a view of the front portion of the burner, shown in. section on the same plane as Fig. 4; and

Fig. 6 is a front elevation of the burner receiving chamber and associated parts.

In the drawings I have shown a pulverized fuel burner of the same general type as that shown in the patent to Craig et al. No. 1,843,662. The embodiment illustrated comprises a horizontal cylindrical fuel nozzle or pipe l0 aligned with a circular opening II in a furnace wall I2 of refractory material. The opening H flares outwardly toward the'rear, and is considerably larger in diameter than the fuel nozzle so that secondary air may enter the furnace around the outside of the fuel stream. The secondary air is preferably supplied under forced draft, and for this purpose a wind-box I4 is mounted on the wall l2- around the opening H, the rate of flow into the windbox being controlled by means of dampers l5. Vanes or louvers l6 surround the opening II to 'distribute the air uniformly about the axis of the burner and to impart a whirling motion to the air. The fuel nozzle I0 is supported at its front end in a sleeve I8 fastened to the front wall of the wind-box. A receiving chamber I9 is mounted on the front end of the sleeve l8, and this receiving chamber is provided with a tangential inlet conduit 20 and a'removable front plate 22. The front plate is somewhat larger in diameter than the fuel nozzle. Vanes 23 are mounted on the plate 22 and inv the path of the,

fuel stream to aid in distributing the fuel uni-' formly about the axis of the pipe II].

In order to'aid in the ignition of the fuel and also obtain a turbulent flame, means is provided at the rear or discharge end of the pipe Ill to,

deflect the fuel outwardly into the surrounding stream of secondary air. For this purpose there is shown a fuel spreader comprising a central hub (Fig. 4) having a series of vanes 26 extending substantially radially outward therefrom. The vanes 26 are preferably of thin sheet metal with their inner ends in planes parallel to the axis of the pipe l0 and their outer portions twisted to an angle of about forty-five degrees with said axis. The twisted portions constitute the major part of the vanes. The hub 25 is preferably cast on to the vanes, the inner ends of the vanes being drilled at 2! to allow the metal of the hub to flow therethrough and provide a firm fastening. The hub 25 is shown mounted on the rear end of a tube 29 coaxial with the pipe IO and closed at its front end by a cap 30. I

Means is provided for adjusting the cross-sectional area available for the flow of the fuel stream past the vanes 26. For this purpose I have shown a series of blades 32 located close to the vanes 26, these parts being relatively adjustable so that the blades obstruct the passages between the vanes to a controlled degree. In the preferred construction illustrated each blade 32 is located close to the front edge of the corresponding vane 2t and arranged to slide relative to said vane in a direction parallel to the axis of the pipe 10. The blades 32 are preferably formed of thin sheet metal, and aresupported at their inner ends by a central hub 33 located in front of and in alignment with the hub 25. This hub 33 may be cast on to the blades, the latter being drilled at 34 to provide an interlocking engagement with the metal of the hub. The blades 32 are located in planes parallel to the axis of the pipe Ill but somewhat offset from said axis, as shown particularly in Fig. 3, so that they contact slidably with the front edges of the vanes. The inner rear portions of the blades are notched at 36 (Fig. 4) to clear the hub 25, and the rear edge 31 of each blade slopes outwardly and rearwardly in a direction substantially parallel to the plane of the vane 26 with which the blade cooperates in controlling the flow area.

It sometimes happens that wisps of straw or particles of rags pass through the pulverizer and r are delivered to the burner with the fuel stream.

In order to prevent such material from obstructing the burner, I preferably slope the front edges 38 of the blades 32 outwardly and rearwardly so that material caught by the blades will slide to their outer ends under the'influence of the air flow. The material may then escape through the slight space between the outer ends of the blades and the surrounding wall of the pipe in, or if necessary the blades may be moved beyond the rearend of the pipe momentarily to allow discharge of the material.

The hub 33 is supported in a manner to facilitate axial adjustment thereof, and for this purpose it is shown mounted on the rear end of a tube 40 closely surrounding the tube 29. Both of these tubes extend through a boss 4| in the front plate 22 of the receiving chamber, and are held in a desired position of adjustment by a set-screw 42 mounted in the boss and extending through a longitudinal slot 43 in the tube 49 into contact with the tube 29, as shown in Fig. 5. A collar 44 is secured to the front end of the tube 40 to form a handle which maybe grasped when adjusting the tube.

It is desirable that each blade 32 remain'substantially in contact with the corresponding vane 26, so that regardless of the position of adjustment the fuel will be given a definite tangeritial motion by reason of the inclined surfaces of the vanes. In order to maintain these parts in proper alignment, a screw 46 is inserted in the wall of the tube 40 near the hub 33 and extends into a longitudinal slot 41 in the tube 29, as shown in Fig. 4.

The operation of the invention will now be apparent from the above disclosure. Pulverized fuel and primary air are delivered to the inlet 20 of the burner, preferably from a pulverizer having a recirculating system of the type disclosed in the patent to Craig No. 1,951,862. The fuel stream flows through the receiving head l9 and the pipe [6 and is discharged through the opening ll into the furnace. Air is delivered to the windbox M by a suitable fan, and after being given a whirling motion by the louvers IS the air enters the furnace around the outside of the fuel stream. As the fuel leaves the pipe I!) it is whirled and thrown. outwardly by the vanes 26 and brought into turbulent contact with the surrounding stream of secondary air, so that combustion is very rapid'and efiicient. Furthermore each of these vanes produces a separate stream comparatively rich in fuel and therefore relatively easy to ignite from the heat of the incandescent refractories in the wall I2. The velocity of the issuing fuel may be controlled by adjusting the tube 40 and the blades 32 axially,

thus varying the area available for flow between the vanes 26. At low ratings the primary air may be reduced by recirculation or otherwise, and still the velocity may be maintained at any desired value by a proper adjustment. To effect an adjustment of the blades, it is of course first necessary to loosen the set-screw 42, which normally holds both the tubes 29 and 40 in a fixed position by forcing the tube 29 against the tube 46 and the latteragainst the boss 4|. Straw or rags which reach the blades 32 will be deflected outwardly by their sloping front edges 38 and thus escape into the furnace. If necessary this may be facilitated by moving the blades rearwardly beyond the end of the pipe ID. By removing the front plate 22 it is possible to withdraw the fuel nozzle, the spreader vanes, and the adjustable blades from the wind-box for inspection or replacement. 7

The burner is comparatively simple and inexpensive to manufacture. It will produce a highly turbulent and efficient flame, and can be easily adjusted for varying" combustion rates. The vanes 26 contact with the fuel stream over a comparatively large area, and hence are effectively cooled. The blades 32 are not only cooled by the fuel stream, but they are also shielded from the radiant heat by the spreader vanes. Practically the entire space in front of the burner is filled with burning fuel, and the combustion is completed very rapidly, so: that the flame is comparatively short and the danger of flame impingement on the furnace walls is minimized.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A fuel burner comprising a nozzle arranged to discharge a stream of fueL means to supply air around the outside of the fuel stream, a series of vanes located in the path of the fuel adjacent the discharge end of the nozzle and each arranged at an angle to the general direction of fuel travel to deflect the fuel outwardly into the surrounding air, and a series of blades mounted adjacent the vanes to restrict the area available for flow between the vanes, the blades and the vanes being relatively adjustable to permit a variation in said area.

2. A fuel burner comprising a nozzle arranged to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, a series of vanes located in the path of the fuel adjacent the discharge end of the nozzle and each arranged at an angle to the axis of the nozzle to deflect the fuel outwardly into the surrounding air, and a series of blades in front of the vanes to restrict the area available for flow between the vanes, the blades and the vanes being relatively adjustable in a generally axial direction to permit a variation in said area.

3. A fuel burner comprising a nozzle arranged to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, a series of vanes located in the path of the fuel adjacent the discharge end of the nozzle and each arranged at an angle to the axis of the nozzle to deflect the fuel, and a series of blades in front of the vanes to restrict the area available for flow between the vanes, each blade extending substantially parallel to the axis of the nozzle and being substantially in contact with the front edge of one of the vanes, the blades and vanes being relatively adjustable in a generally axial direction to permit a variation in said area.

4. A fuel burner comprising a nozzle arranged to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, a series of vanes extending in substantially radial directions across the path of the fuel as it leaves the nozzle, each vane being arranged at an angle to the axis of the nozzle to deflect the fuel outwardly into the surrounding air, and a series of blades in front of the vanes to restrict the area available for flow between the vanes, each blade being substantially in contact with the front edge of one of the vanes, the blades and vanes being relatively adjustable in a generally axial direction to permit a variation in said area.

5. A fuel burner comprising a nozzle arranged to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, a series of vanes extending in substantially radial directions across the path of the fuel as it leaves the nozzle, each vane being arranged at an angle to the axis of the nozzle to deflect the fuel outwardly into the surrounding air, and a series of blades in front of the vanes to restrict the area available for flow between the vanes, each blade extending substantially parallel to the axis of the nozzle and being substantially in contact with the front edge of one of the vanes, the blades and vanes being relatively adjustable in a generally axial direction to permit a variation in said area.

6. A fuel burner comprising a cylindrical nozzle arranged to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, a series of vanes extending in substantially radial directions across the path of the fuel as it leaves the nozzle, each vane being arranged at an angle to the axis of the nozzle to deflect the fuel outwardly into the surrounding air, supporting means for said vanes extending axially of the nozzle, a series of blades in front of the vanes to restrict the area available for flow between the vanes, each blade extending substantially parallel to the axis of the nozzle and being substantially in contact with the front edge of one of the vanes, and a tube supporting said blades and surrounding the vane supporting means, said tube and vane supporting means being relatively adjustable axially to permit a variation in said area.

7. A fuel burner comprising a receiving cha her having a removable plate at the front thereof, a fuel inlet passage leading to the receiving chamber, a cylindrical nozzle extending rearwardly from the receiving chamber to discharge a stream of fuel rearwardly, means to supply air around the outside of the fuel stream, two coaxial tubes mounted Within the nozzle and extending forwardly through the removable plate, a series of vanes supported by the inner tube adjacent the rear end of the nozzle, each vane extending substantially radially across the path of the fuel and being arranged at an angle to the axis of the nozzle to deflect the fuel outwardly into the surrounding air, and a series of blades supported by the outer tube, each blade extending substantially parallel to the axis of the nozzle and. being substantially in contact with the front edge of one of the vanes, the tubes being relatively adjustable axially to vary the extent to which the blades restrict the area available for flow between the vanes, the removable plate being sufficiently large to permit withdrawal of the blades and vanes forwardly through the receiving chamber.

ALBERT G. BLODGETT. 

